Set a = {1,3,5,7,9...}, expressed by description A = {x | x = 2K + 1, k = n} why 2k-1 is not good

Set a = {1,3,5,7,9...}, expressed by description A = {x | x = 2K + 1, k = n} why 2k-1 is not good

It's a pleasure for you
The set represents a set of positive odd numbers~
So it is a = {x | x = 2K + 1, K belongs to n}
Of course, the odd number can also be represented by 2k-1, but in this way, the value range of K needs to be changed~
A = {x | x = 2k-1, K belongs to n *}~
If you are not clear, you are welcome to inquire and exchange, hoping to help the landlord~

Using description method to express set B = {1,3,5,7,9} as

B = {x | x = 2Y + 1, y is a non negative integer}
This is for the general situation. If there are only five numbers, please modify them

Representation of set a = {1,2 / 3,3 / 5,4 / 7,5 / 9} by description

｛x | x=n/(2n-1) ,1

Representation of set {1, - 3,5, - 7,9, - 11} by description
My answer seems to be: {x = (- 1) & # 710; 2 (2n + 1), n belongs to N, n ≤ 5}
But I did. It seems wrong

Description method: {x | (x-1) (x + 3) (X-5) (x + 7) (X-9) (x + 11) = 0}

Representation of set {1 / 2,3 / 4,5 / 6,7 / 8 }Get
Why?

(x = 2N-1 / 2n is a positive integer)

Representation of set {2,4,6,8} {1,1 / 2,1 / 3,1 / 4} by description
Representation of set {2,4,6,8} by description
{1,1/2，1/3,1/4}

{2,4,6,8}={x I x=2n,1≤n≤4,n∈N}
{1,1/2,1/3,1/4}={x I x=1/n,1≤n≤4,n∈N}

The set a = {1,2,4,8,16,...} can be expressed as

A={x|x=2^n,n∈N}

The following sets are represented by Description: ① {1,4,7,10,13} ② {- 2, - 4, - 6, - 8, - 10}

1. {x | x = 3K + 1, K ∈ N and K ≤ 4}
2. {x | x = - 2K ∈ n * and 5 ≥ K ≥ 1}
I'm not a teacher,

Describe the following two sets
①{0,±1/2,±2/5 ,±3/10,±4/17,…… }
②{1,5,25,625}

① {n | positive and negative n / (n square + 1) n ≥ 0, n ∈ Z}
② {x | 5 to the power of X, X ≥ 1, X ∈ Z}

Describe the following sets
The set of all points inside the circle x ^ 2 + y ^ 2 = 36 (excluding the circle)

Description {(x, y) | x ^ 2 + y ^ 2